Support is requested for a Keystone Symposia meeting entitled HIV Vaccines, organized by Georgia D. Tomaras, Quentin J. Sattentau, and Barbara L. Shacklett. The meeting will be held in Keystone, Colorado from February 10 - 15, 2013. Recent data in both humans and non-human primates suggest that a clinically useful HIV-1 vaccine is possible and that the use of therapeutic interventions can be an efficacious prevention strategy. The path forward will require a detailed understanding of the correlates of protection to HIV-1/SIV and the development of better immunogens to induce specific and long lasting immunity. Moreover, the role of vaccine elicited immune responses to prevent the initial stages of HIV-1 infection at mucosal sites will be critical toward understanding protective immunity. Scientific expertise from vaccine trials and studies of long term immunity will help inform decisions in the path to the induction of immunity by an HIV-1 vaccine. Furthermore, a better understanding of how to target an efficacious vaccine in diverse populations will require more detailed studies of host genetics, innate immune responses, the effect of therapeutic interventions, and other host factors (that can affect the development of robust immune responses and/or the analysis of HIV-1 vaccine trials). At this meeting, leading experts from both within and outside the HIV field will present findings from recent advances in human and non-human primate trials on immune mechanisms of protection as well as implementation of efficacious vaccines and other preventative strategies in diverse populations. Opportunities for interdisciplinary interactions will be significantly enhanced by the concurrent meeting on B Cell Development and Function - which will share a keynote session and two plenary sessions with this meeting. This pairing is explicitly designed to enhance opportunities for exchanges between researchers who do not typically interact. In this regard, it must be emphasized that a major roadblock in our efforts to generate a successful HIV vaccine relates to our limited knowledge of the B cell subsets and signals required for the production of protective class-switched and hypermutated neutralizing antibodies in systemic and mucosal lymphoid organs.